Background of the Invention
Field of the Invention
[0001] This invention relates to the art of print heads.
Brief Description of the Prior Art
[0002] Applicant's prior U.S. patent 4,173,184 granted November 6, 1979, U.S. patent No.
3,783,083 to W. A. Jenkins, dated January 1, 1974, and U.S. patent No. 3,783,786 to
L. E. Ellison et al dated January 8, 1974 are made of record.
Summary of the Invention
[0003] The invention relates to an improvement to the apparatus disclosed in applicant's
U.S. patent No. 4,173,184.
[0004] When printing characters which are designed to be machine-readable, it is essential
that the printed data or characters be of the highest quality to assure that the characters
can be read by the machine. According to the invention, there is provided a low-cost
print head with a stationary support of integral molded plastics construction with
no moving parts which provides detenting superior to that accomplished by the device
according to patent 4,173,184. When advancing the printing band of prior patent No.
4,173,184 to bring a selected printing block to the printing position, the user is
aware that the selected printing block is approaching the position at the printing
zone and hence reduces the amount of turning force being applied to the selector.
When the selected printing block reaches the printing zone, the leading end face contacts
one of the abutment shoulders to arrest the movement of the printing band. It sometimes
happens, due to the elastomeric material of which the printing band is composed and
due to the fact thlt the lugs are quite thin so that the shoulders of each lug are
very small, that the lug at the printing zone compresses slightly so that the selected
printing block overtravels the desired stopping point at the printing zone just slightly.
[0005] It has been found that by providing the support with a pair of pocket-forming abutment
shoulders which meet abruptly with respective supporting lands and by providing an
additional pair of abutment shoulders terminating at abrupt edges for cooperating
with end faces of next adjacent lugs that the detenting is outstandingly effective
without increasing the thickness of the lug or the number of parts used in the support
of patent No. 4,173,184.
[0006] According to a specific embodiment of the invention, the abutment shoulders at the
pocket join the lands at a pair of abrupt edges and the support includes an additional
pair of abutment shoulders terminating at an additional pair of abrupt edges. The
entire or complete end face of one of the lugs abuts one abutment shoulder at the
pocket and the entire or complete end face of an adjacent lug abuts one of the additional
abutment shoulders to stop the advance of the printing band when the printing band
is advanced to where the selected printing block is at the printing zone. More particularly,
the one abutment shoulder at the pocket contacts the root of the end face of the lug
under the printing block at the printing zone and one additional abutment shoulder
contacts the root of the end face of one of the lugs adjacent the pocket. Because
the movement of the printing band in either direction is stopped by a pair of spaced
abutment shoulders, the printing band does not advance to a position where the selected
printing block has over-traveled the printing position.
Brief Description of the Drawings
[0007]
FIGURE 1 is a perspective view of a fragmentary portion of a print head;
FIGURE 2 is an enlarged side elevational view of the print head shown in FIGURE 1;
FIGURE 3 is an enlarged side elevational view showing the manner in which a printing
element of a printing band is supported by a support at the printing zone;
FIGURE 4 is an enlarged fragmentary view showing a portion of a drive wheel and a
portion of the printing band;
FIGURE 5 is a perspective view of the wheel;
FIGURE 6 is a fragmentary view taken along line 6--6 of FIGURE 2;
FIGURE 7 is a side elevational view of an alternative embodiment; and
FIGURE 8 is a view similar to FIGURE 3, showing applicant's invention.
Description of the Preferred Embodiments
[0008] With reference to FIGURE 1, there is shown a fragmentary portion of a print head
generally indicated at 10. The print head 10 includes a print head body or frame 11
having a transversely extending arcuate portion or saddle 12 in which wheels 13 are
rotatably mounted. The body 11 includes a support 14. Printing bands generally indicated
at 15 are trained or received about the support 14 and the respective wheels 13 so
that each printing band 15 is capable of being driven by its respective drive wheel
13. A selector 16 rotatably mounted on a shaft 17 can be coupled with one wheel 13
at a time so that the wheels 13 can be selectively driven and consequently the selected
printing band 15 is rotated about the support 14 the selected distance. The printing
bands 15 are under slight tension. Each printing band 15 has a printing section 18
and a corresponding human readable non-printing section 19 so that when a selected
printing element 20 is disposed at the printing zone Z as shown in FIGURE 2, then
a corresponding human readable character can be sighted through a window 21. Hinges
22 connect adjacent printing blocks or elements 20. The underside of both the printing
and human readable sections 18 and 19 are provided with lugs 23. The lugs 23 preferably
are generally flat and smooth on their undersides and terminate at opposed ends at
generally parallel end faces 24. Each of the lugs 23 has the same length and lugs
23 are equally spaced apart. Reinforcing material such as nylon cords 20" are shown
to pass through the printing elements 20 and the hinges 22 of each individual band
15. The bands 15 are molded with elastomeric material. Each band 15 ca,
1 yield resiliently as it is advanced upon rotation of wheel 13. The support 14 has
a transversely extending notch or pocket 25 for receiving a lug 23 of each printing
band 15 at the printing zone Z. The notch 25 has a pair of opposed shoulders 26 which
are generally parallel to each other. The shoulders 26 are spaced apart by a distance
approximately equal to the length of a lug 23 before the lug 23 is received in the
socket 25. The lugs 23 are preferably slightly longer, for example 0.001 inch, than
the distance between the shoulders 26 so that there is a slight interference fit therebetween.
When a printing element 20 is at the printing zone there is one and only one location
and orientation for that printing element 20 which is in effect "plugged in" by means
of its respective lug 23 to the notch 25. Thus, in moving the printing band 15 to
the selected position, there is no tendency whatever for the printing band to creep
partly out of the pocket or notch 25 into which it snaps.. As best shown in FIGURE
3, the support 14 has opposed tapered entries 27 and 28 and lands 29 and 30 formed
on support members 29' and 30' which terminate at the respective shoulders 26. The
lands 29 and 30 support the hinges 22 at each side of the printing element 20 which
is disposed at the printing zone Z. The arrangement of the support shoulders 26, the
end faces 24, and the support that lands 29 and 30 provide to the hinges 22 results
in excellent detenting of the printing bands 15 so that each selected printing element
20 is properly registered at the printing zone Z. The lands 29 and 30 are slightly
radiussed at 31 and 32 where they join the shoulders 26. Accordingly, the printing
characters 20' of the respective printing elements 20 are capable of making a quality
printing impression on a record R disposed on a platen 33 when the print head 10 and
the platen 33 move into cooperation with each other. With reference to FIGURE 4, the
wheel 13 is shown to have spaced apart notches or channels 34. Notches 34 have spaced
apart shoulders 35. It is preferred that the shoulders 35 of each notch 34 be generally
parallel to each other and that they be spaced apart by a distance substantially equal
to the length of the respective lugs 33. Accordingly, the end faces 24 of the printing
bands 15 abut the shoulders 35 of the wheels 13 essentially squarely. In addition,
peripheral extent E of arcuate lands 36 between adjacent notches 34 is approximately
equal to the length of the respective hinges 22. As best shown by extension lines
PL in FIGURE 4, the shoulders 35 are generally parallel to each other. The lugs 23
are spaced from the bottom of the respective notches 34. The human readable characters
19' and printing elements 20 can extend along chords of the circle defined by its
wheel 13. Therefore, any printing elements 20 disposed at the wheel 13 cannot acquire
a predetermined curvature. The flexure in the band 15 takes place at the hinges 22.
The hinges 22 are relatively thin as compared with the combined thickness of the printing
element 20 and its associated lug 23.
[0009] The embodiment of FIGURE 7 is identical to the embodiment of FIGURES 1 through 6,
except that the band 15a has only a printing section 18a but no human readable section.
The printing section 18a extends for substantially the entire length of the band 15a.
It is apparent that because of the configuration of the wheel 13, all the bending
takes place in hinges 22a. Hence the printing elements 20a disposed at the wheel cannot
acquire a predetermined curvature. The hinges 22a are also relatively thin as compared
with the combined thickness of a printing element 20a and its associated lug 23a.
[0010] In the above embodiments, the lugs 23 and 23a are about 0.145 inch in length, and
the lugs 23 and 23a are about 0.01 inch thick measured from the undersides of the
hinges and preferably less than about .02 inch thick. Lugs 23 and 23a are spaced apart
about 0.062 inch.
[0011] Further details of the selector 16 and wheels 13 are disclosed in above mentioned
U.S. patent No. 3,783,083.
[0012] With reference to FIGURE 8, there is shown a fragmentary portion of a print head
body or frame 40, and the fragmentary portion of a printing band generally indicated
at 19. Except for support 41, the embodiment of FIGURE 8 is identical to the embodiment
of FIGURES 1 through 6. The support 41 includes a pair of support members 42 and 43.
The support members 42 and 43 have tapered entries 44 and 45 which terminate at supporting
lands 46 and 47. The support 41 has a pair of abutment shoulders 48 and 49 which joint
the respective lands 46 and 47 at abrupt edges 50 and 51. The lug 23 has a pair of
end faces 24 and 24' which join the underside of the printing block at respective
roots 52 and 52. The support 41 also has an additional pair of abutment shoulders
54 and 55. The abutment shoulder 54 is shown to be in complete contact with the end
face 24' of a respective lug 23 and the shoulder 55 is shown to be in complete contact
with the end face 24 of another lug 23. More particularly, the shoulders 54 and 55
join the tapered entries at abrupt edges 56 and 57. The abrupt edges 56 and 57 are
shown to contact the roots 52 and 53.
[0013] When the selector 16 is rotated to advance a respective wheel 13, the printing band
19 can be advanced in the direction according to arrow A. When the selected printing
block 20 has reached the printing position or printing zone Z, and the user lessens
the advancing force applied to the selector 16, the end face 24 contacts the abutment
shoulder 48 and simultaneously therewith the end face 24 of an adjacent lug 23 contacts
the abutment shoulder 55, thereby stopping the motion of the printing band 19 with
the selected printing block 20 registered precisely with the printing zone Z. In this
position, the other abutment shoulders 49 and 54 are also in contact with end faces
24' of the respective lugs 23.
[0014] In the event the printing band 19 is advanced in the direction of arrow A' to bring
a selected printing block 20 to a printing position, the end faces 24' will abut respective
abutment shoulders 49 and 54 to arrest the movement of the printing band 19, thereby
bringing the selected printing block 20 precisely to the printing position in precise
detented relationship with respect to the support 41 and the other printing blocks
20 of the other printing members 19.
[0015] As seen in FIGURE 8, the roots 52 and 53 are slightly radiussed, when not engaged
by an abrupt edge. However, the abrupt edges 50, 57 and 51,56 compress the elastomeric
material at the respective roots 52 and 53 as shown. Optimally, the abrupt edges 50,
51, 56 and 57 are not radiussed.
[0016] Other embodiments and modifications of this invention will suggest themselves to
those skilled in the art, and all such of these as come within the spirit of this
invention are included within its scope as best defined by the appended claims.
1. In a print head comprising a stationary support (41), the support including a pair
of spaced support members (42, 43) having respective lands (46, 47) and tapered entries
(44, 45) joined to the lands, the support members having abutment shoulders (48, 49)
joining the lands and defining a pocket for receiving a lug (23), a series of rotatably
mounted wheels (13), a series of printing bands (15) trained about the wheels and
the support, means (16) selectively engageable with any printing band for advancing
the respective printing band in either direction, each printing band having a plurality
of printing blocks (20), the printing blocks of each band having a plurality of different
printing elements (20'), hinges (22) joining the printing blocks, a lug (23) at the
underside of each printing block, each lug having a pair of spaced end faces (24,
24'), the end faces being joined at their roots (52, 53) to the undersides of the
respective printing blocks, and each lug being selectably received and detented in
the pocket with its respective end faces (24, 24') in abutment with the abutment shoulders
(48, 49), the detenting characterized in that the abutment shoulders join the lands
at a pair of abrupt edges (50, 51), the support having an additional pair of abutment
shoulders (54, 55) terminating at an additional pair of abrupt edges (56, 57) so that
advance of the printing band in one direction is stopped by one abutment shoulder
and one additional abutment shoulder contacting the roots of end faces of adjacent
lugs or advance of the printing band in the opposite direction is stopped by the other
abutment shoulder and the other additional abutment shoulder contacting the roots
of end faces of adjacent lugs.
2. In a print head comprising a stationary support (41), the support including a pair
of spaced support members (42, 43) having respective lands (46, 47) and tapered entries
(44, 45) joined to the lands, the support members having abutment shoulders (48, 49)
joining the lands and defining a pocket for receiving a lug (23), a series of rotatably
mounted wheels (13), a series of printing bands (15) trained about the wheels and
the support, means (16) selectively engageable with'any printing band for advancing
the respective printing band in either direction, each printing band having a.plurality
of printing blocks (20), the printing blocks of each band having a plurality of different
printing elements (20'), hinges (22) joining the printing blocks, a lug (23) at the
underside of each printing block, each lug having a pair of spaced end faces (24,
24'), the end faces being joined at their roots (52, 53) to the undersides of the
respective printing blocks, and each lug being selectably received and detented in
the pocket with its respective end faces (24, 24') in abutment with the abutment shoulders
(49), the detenting characterized in that the abutment shoulders join the lands at
a pair of abrupt edges (50, 51), the support having an additional pair of abutment
shoulders (54, 55) terminating at an additional pair of abrupt edges (56, 57) so that
advance of the printing band in one direction is stopped by one abutment shoulder
and one additional abutment shoulder contacting the roots of end faces of adjacent
lugs or advance of the printing band in the opposite direction is stopped by the other
abutment shoulder and the other additional abutment shoulder contacting the roots
of end faces of adjacent lugs, wherein the abutment shoulders defining the pocket
are generally parallel, and wherein the additional abutment shoulders lie in a flat
plane generally perpendicular to the abutment shoulders.
3. In a print head comprising a stationary support (41), the support including a pair
of spaced support members (42, 43) having respective lands (46, 47) and tapered entries
(44, 45) joined to the lands, the support members having abutment shoulders (48, 49)
joining the lands and defining a pocket for receiving a lug (23), a series of rotatably
mounted wheels (13), a series of printing bands (15) trained about the wheels and
the support, means (16) selectively engageable with any printing band for advancing
the respective printing band in either direction, each printing band having a plurality
of printing blocks (20), the printing blocks, of each band having a plurality of different
printing elements (20'), hinges (22) joining the printing blocks, a lug (23) at the
underside of each printing block, each lug having a pair of spaced end faces (24,
24'), the end faces being joined at their roots (52, 53) to the undersides of the
respective printing blocks, and each lug being selectably received and detented in
the pocket with its respective end faces (24, 24') in abutment with the abutment shoulders
(48, 49), the detenting characterized in that the abutment shoulders join the lands
at a pair of abrupt edges (50, 51), the support having an additional pair of abutment
shoulders (54, 55) terminating at an additional pair of abrupt edges so that advance
of the printing band in one direction is stopped by one abutment shoulder and one
additional abutment shoulder contacting the roots of end faces of adjacent lugs or
advance of the printing band in the opposite direction is stopped by the other abutment
shoulder and the other additional abutment shoulder contacting the roots of end faces
of adjacent lugs, wherein the additional shoulders lie in a flat plane.
4. In a print head comprising a stationary support (41), the support including a pair
of spaced support members (42, 43) having respective lands (46, 47) and tapered entries
(44, 45) joined to the lands, the support members having abutment shoulders (48, 49)
joining the the lands and defining a pocket for receiving a lug (23), a series of
rotatably mounted wheels (13), a series of printing bands (15) trained about the wheels
and the support, means (16) selectively engageable with any printing band for advancing
the respective printing band in either direction, each printing band having a plurality
of printing blocks (20), the printing blocks of each band having a plurality of different
printing elements (20'), hinges (22) joining the printing blocks, a lug (23) at the
underside of each printing block, each lug having a pair of spaced end faces (24,
24'), the end faces being joined at their roots (52, 53) to the undersides of the
respective printing blocks, and each lug being selectably received and detented in
the pocket with its respective end faces (24, 24') in abutment with the abutment shoulders
(48, 49), the detenting characterized in that the abutment shoulders join.the lands
at a pair of abrupt edges (50, 51), the support having an additional pair of abutment
shoulders (54, 55) terminating at an additional pair of abrupt edges (56, 57) so that
advance of the printing band in one direction is stopped by one abutment shoulder
and one additional abutment shoulder contacting the roots of end faces of adjacent
lugs or advance of the printing band in the opposite direction is stopped by the other
abutment shoulder and the other additional abutment shoulder contacting the roots
of end faces of adjacent lugs, wherein the abrupt edges are molded as an integral
part of the support.
5. In a print head comprising a stationary support (41), the support including a pair
of spaced support members (42, 43) having respective lands (46, 47) and tapered entries
(44, 45) joined to the lands, the support members having abutment shoulders (48, 49)
joining the lands and defining a pocket for receiving a lug (23), a series of rotatably
mounted wheels (13), a series of printing bands (15) trained about the wheels and
the support, means (16) selectively engageable with any printing band for advancing
the respective printing band in either direction, each printing band having a plurality
of printing blocks (20), the printing blocks of each band having a plurality of different
printing elements (20'), hinges (22) joining the printing blocks, a lug (23) at the
underside of each printing block, each lug having a pair of spaced end faces (24,
24'), the end faces joining the undersides of the respective printing blocks, and
each lug being selectably received and detented in the pocket with its respective
end faces (24, 24') in abutment with the abutment shoulders (48, 49), the detenting
characterized in that the abutment shoulders join the lands at a pair of abrupt edges
(50, 51), the support having an additional pair of abutment shoulders (54, 55) terminating
at an additional pair of abrupt edges (56, 57) so that advance of the printing band
in one direction is stopped by one abutment shoulder and one additional abutment shoulder
contacting the complete end faces of adjacent lugs or advance of the printing band
in the opposite direction is stopped by the other abutment shoulder and the other
additional abutment shoulder contacting the complete end faces of adjacent lugs.